Treatment of metal



Sept. 27, 1938.

S. R. M BRIDE TREATMENT OF METAL Filed Feb. 11, 1936 I INVENTOR.

ATTORNEYfi,

52 awa q, 52

Patented Sept. 27, 1938 V PATENT OFFICE 2,131,062 TREATMENT or METALSamuel Ross McBride, Ravenna,;hio, assignor to H. L. F. Company, LosAngeles, Cali1'., a corporation of California Application February 11,1936, Serial No. 63,385

' 1 Claim. (Cl. 22-212) In the preparation of metals for certain uses ithas been customary to mechanically work the. metal, such as by rolling,which for example is the particularly feasible large scale commercialmethod. This has been necessary by reason of the fact that metal as castis essentially crystalline and of poor and irregular texture, and beingdeficient in tensile strength. Chill-casting, while providing aparticular surface-hardness has aggravated the difliculties in otherdirections. In

accordance with the present invention however, it now becomes possibleto treat metal to attain mechanical properties of peculiarlyadvantageous character, and in a manner readily applicable.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described, andparticularly pointed out in the claim, the following description and theannexed drawing setting forth in detail certain illustrative embodimentsof the invention, these being indicative however, of but a few of thevarious ways in which the principle of the invention may be employed.

In said annexed drawing: Fig. 1 is a perspective view of apparatuscontemplated in the invention; Fig. 2 isa similar view of furtherdetail; and Fig. 3' is a fragmentary sectional view of mold-wallstructure.

In working metal by rolling, the structure is in effect compressed inone direction and the grain structure is correspondingly elongated. Onthe other hand, in casting as customarily practiced,

the grain structure or crystalline detail takes its positionpromiscuously, and generally within the body of the mass the crystallinesize reaches con- I siderable magnitude. Where. the metal is chillcast,the growth of large crystalline structure at the surface is prevented,but the mass of the metal internally is irregular. In accordance withthe present invention, metal is subjected to what is in effect themolecularly drawing of the metal progressively by changing it from theliquid to solid state by an advancing front through the mass treated.Formation of macro-crystalline structure is thus impossible, andcompression or drawing action is applied progressively and regularly insitu. 'In this, whereas in rolling for instance, compression is appliedin one dimensional direction, by the present procedure the com-,pressional action is simultaneously efiected in both dimensionaldirections for any given section plane. The metal thus treated bycontrolled progressive molecular drawing action is characterized byproperties none .of which have been known to cast products, and some ofwhich have not been heretofore attained by any known procedure. It thusbecomes possible to produce structures of unique properties, and wherelongknown' alloys are treated, metal products with 5 newly adapted,utilities may be had. For instance aluminum alloys as prevalently castinto cylinder heads for internal combustion engines, which haveheretofore been characterized by theutmost unevenness of texture,exaggerated grain and ir- 10 regular brittleness, when formed intosimilar shapes by the present invention are characterized by anoutstanding evenness of texture and great toughness. Similarly, brassand bronze alloys in accordance herewith yield products having en- 15hanced tensile strength and evenness of texture. With all of these also,the Brinell hardness may be controlled to particularly advantageousdegree.

The casting molds here employed have a wall 20 structure which is notcapable of storingsubstantial amounts of heat. Physically, the moldwalls are in general quite thin, and the heat-control is efiected bytemperature change progressively applied. Asillustrated in Fig. 1, thereis shown 25.

a mold 2 of very thin wall structure, this being mounted on a suitablesupport 3; and there being suitable sprue access 4 to the mold cavity.While.- a progressing cooling zone may be provided by progressivelyrelatively raising a water level about 30 the mold, I prefer a travelingtemperature-control means comprising a jetting device 5, in suitableform, for instance an annular hollow tube with multi-perforationsdirected radially inwardly toward the mold, and having a flexibletubular 3 connection 6 to a suitable source of cooling fluid,

the traveling evice being mounted to slide on a guide I and eingpropelled advancingly by a driving meansr as for instance a screw-stem 8which is drive through bevel gearing 9 and re- 40 duction gearin Ill byamotorl I.

The molten etalis poured into the mold 2, and the tempo ature controldevice 5 is set inmotion by the otor I I, and progressively travels fromthe bottom to the top, jetting the cooling fluid against the wallsof'the mold, and correspondingly'abstracting the heat therewithin andsetting the metals in a gradually progressing manner. The cooling fluidwill depend somewhat upon .the particular metal being :treated.

While for quite low meltingpoint alloys jets of cold air are suitable,in general water or some aqueous solutionds suppliedthrough the coolingring 5. Where itis desired, the progressive cooling action may be'applied to a part of the mold instead of its entirety, and in generalthe action The latter, depending upon the thickness of section of metalto be cast may beof greater or less section. Thus, with the casting ofmoderate size ingots. a painted-on coating about 1?; inch thick, ofrefractory material, such as magnesium oxide with a binder issatisfactory. A particularly advantageous lining material is acomposition of zirconium oxide and magnesium oxide, the latter beingpredominant, and this is satisfactory for large scale ingot casting, acoating of lining inch thick being advantageous as sufficient protectionfor the metal shell. The magnesia and the like may be made up withphosphoric acid or other binders such as sodium silicate etc. Otherrefractory materials, as sillimanite, bauxite, kaolin. etc., may beused, alone or in mixture. The metal shell for heavy ingot casting maybe of thickness about. inch advantageously.

Slightly different effects may beattained, depending upon whether ,theprogressive temperature controlling action be started immediately orafter allowing the molten metal to stand for a short time. This woulddepend also upon the particular metal or alloy being cast. By advancingthe cooling zone such that the in-pouring metal raises its level inadvance of the traveling cooling zone, such lead of temperaturedifferential allows all gases to escape, and the cooling area or sectionis at all times amply supplied with filling-metal, and a fine eventexture free from porosity and piping is had, while the hardness of thecasting is approximately the same through its entire cross'section. Insome cases, it is advantageous to apply a heating means 15 to the topportion of thev mold, so as to maintain a highly fluent condition of themetal continuously at this point while the progressing wave of settingup traverses the body. Preliminary heating of the entire mold or heatingthe mold progressively before the rising level of the incoming metal isin fact advantageous in certain cases.

Where a core is required, as for instance core l2, Fig. 2, it may beheld below in a support it and above by adjusting screws I4.

As illustrating the niceties of gradation of properties here possible, abronze alloy of for instance 70 per cent copper, 8 per cent tin, and 22per cent lead, where cast into bearing pieces of cylindrical orsemi-cylindrical contour, with the cooling wave started immediately fromthe bottom of the mold progressively to the top, yields a product inwhich the cellular wall structure of the copper-tin matrix is very thin.While, 11' the same alloy is allowed to stand in the mold one-half aminute before the temperature-control device is started on its travel up themold, the cellular walls of the copper-tin matrix are heavier and thelead is not so finely dispersed. This difference in structure effects adiiferenoe in the wearing qualities of the bearing bronze. The hearingwhich is immediately treated as above noted, will wear more rapidly thanthe bearing with the delay-treatment, but will cause less wear of. theshaft which is supported. Such difierences in wearing life areadvantageous in some usages, and a successful manner of attainingprecisely conrolled results is thus very important.

With some shapes of desired metal products,- the controlled progressivecooling of the metal may be best effected from the interior. Thus, ahollow body may be arranged with traveling cooling-head in the core.

As illustrative of products attainable, a few instances may be noted. Analloy of 70 per cent copper, 8 per cent tin, and 22 per cent lead whenthus cast has a Brinell hardness 65-70, tensile strength 29,000-31,000,and compression 26,000-29,000. This same alloy when cast in sand byconventional practice has Brinell hardness 48-52, tensile strength23,000-24,500, and compression 14,000-16,000. An alloy of 88 per centcopper, 8 per cent tin," and 4 per cent lead when cast in a sand mold byordinary procedure, has a Brinell hardness 60-65, elastic limit18,000-21,000,.

ultimate 28,000-32,000, and elongation in 2 inches 18-20. But, the samealloy when treated in accordance with the present invention has aBrinell hardness 93-98, elastic limit 22,000-25,000, ultimate41,000-43,000, elongation in 2 inches 15-16. Again, a brass (66 per centcopper and 34 per cent zinc) when produced by the old methods, ascasting and then hard rolling, has an elongation 4-5, tensile strength56,000-61,000, and Brinell hardness 71-75. The same brass alloy whentreated in accordance with the present invention has an elongation 7-8,tensile strength 54,000-59,000, and Brinell hardness 75-78, thusrepresenting a combination of properties not attainable by hard rolling,and having however tensile strength which is comparable. A gear bronzealloy (89 per cent copper and 11 per cent tin), when treated by myprocess has an elastic limit 30,000-31,000, ultimate 50,000-52,000,elongation 9-1-10, reduction of area 7-8, and Brinell hardness 100-102.Again, electrolytic copper where ingot-cast in accordance with ordinarypractice is of very uneven texture and low tensile strength, but whentreated in accordance with the present invention has a tensile strengthof 37,000-39,000, elongation 36-39, and reduction of area 47-52. Grayiron (silicon 2.80, total carbon 3.25, and manganese 0.60) whenformed-in cylindrical shapes in accordance with the present inventionfor pump liners has a Brinell hardness 210-212, and compression115,000-118,000. It is notable also that it is hereby possible to useeven quite poor grades of metaland still get good texture products.customarily for instance there is great particularity in the choosing ofmetal free from phosphorus and the like, in order to prevnt excessivelypoor structure.

The refinement of texture now attainable how- F., or as low as possible,in order to keep the lead segregating. The products have had Brinellhardness of 60-65. Such alloys could not from be handled in chill moldsat all. on account of scaling and blistering. With the presentprocedure, I can pour these alloys at 2350" F., and the texture isoutstandingly better. Thus, such a high lead alloy per cent lead, 5 percent tin, 70 per cent copper) yields a Brinell hardness of 15-80. Again,if a hard bushing alloy (88 per cent copper) be cast in sand at2000-2050 F. as

in the old practice, the product has Brinell hardness 60-66. Treatedhowever by the present process, and poured at a temperature of 2350".F.,

the product has a Brinell hardness of 100. The wearing life'of such abushing is 3-4 times longer than that of the former. a

The specific gravity of products of the present" procedure is notablyhigher than that of products of sand molding or chilled molding. Withbronze bushings for instance, this is an 8 per cent increase. Theincrease in specific gravity is the result of the higher density due tothe compression-action impressed upon the metal by the progressivesetting-up wave in its controlled course. Such compression here howeveris further bi-dimensionally exerted progressively on the metal section,instead of mono-dimensionally as in the rolling process. Thus it is,that not withstanding the greater simplicity of treatment, productscompare favorably as to tensile strength with rolled products asheretofore had, and. besides aflord additional characteristics notattainable in rolled products.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in the following claim, or the equivalent of such, beemployed.

I1 therefore, particularly point out and distinctly claim as myinvention:

A device for treating metals, which comprises a ring member comprising aplurality of jets for fluid arranged in a common plane, a movablecarrier therefor, flexible connections from a source of fluid-supply tosaid Jets, acylindrical mold with a wall having substantially noinherent capacity for-chilling molten metal in contact with it, saidmold being exposed to said jets, and means for controllably moving saidring of jets progressively along the wall of said mold coordinated withthe pouring or the metal into the

